Pointer device, electronic watch, control method for pointer device, and recording medium

Abstract

An electronic watch includes a pointer; a stepping motor including a coil and configured to drive the pointer; a driving circuit configured to drive the stepping motor; an A/D converter configured to detect electromotive force generated in the coil due to an impact; and a CPU configured to control driving of the driving circuit. The CPU determines a direction in which the pointer is likely to be shifted, based on the electromotive force detected by the A/D converter, determines whether the pointer is shifted due to the impact, and upon determining that the pointer is shifted, corrects a position of the pointer in accordance with the direction in which the pointer is likely to be shifted.

The invention claimed is: 
     
       1. A pointer device comprising:
 a pointer; 
 a stepping motor comprising a coil and configured to drive the pointer; 
 a driving circuit configured to drive the stepping motor; 
 a detection unit configured to detect electromotive force generated in the coil due to an impact; and 
 at least one processor configured to control driving of the driving circuit, wherein the at least one processor is configured to:
 determine a direction of a first peak of the electromotive force detected by the detection unit; 
 determine a total number of a second or subsequent peaks of the electromotive force detected by the detection unit, wherein each of the second or subsequent peaks of the electromotive force is a peak in the opposite direction to a peak immediately preceding the each of the second or subsequent peaks; 
 determine whether the total number is an even number; 
 determine whether the pointer is shifted in a shifting direction corresponding to the direction of a first peak of the electromotive force based on the direction of the first peak of the electromotive force and a result of the determination of whether the total number is the even number; and 
 upon determining that the pointer is shifted in the shifting direction, correct a position of the pointer in accordance with the shifting direction. 
 
 
     
     
       2. The pointer device according to  claim 1 ,
 wherein the at least one processor is configured to not correct the position of the pointer when the first peak of the electromotive force detected by the detection unit is in a positive direction, and the peak to be counted is detected for an odd number of times, and correct the position of the pointer when the peak to be counted is detected for an even number of times. 
 
     
     
       3. The pointer device according to  claim 2 ,
 wherein the at least one processor is configured to, when the first peak of the electromotive force detected by the detection unit is in the positive direction and the peak to be counted is detected for an even number of times, move the pointer in a reverse rotation direction to correct the position of the pointer. 
 
     
     
       4. The pointer device according to  claim 1 ,
 wherein the at least one processor is configured to correct the position of the pointer when the first peak of the electromotive force detected by the detection unit is in a negative direction and the peak to be counted is detected for an odd number of times, and does not correct the position of the pointer when the peak to be counted is detected for an even number of times. 
 
     
     
       5. The pointer device according to  claim 4 ,
 wherein the least one processor is configured to, when the first peak of the electromotive force detected by the detection unit is in the negative direction and the peak to be counted is detected for an odd number of times, move the pointer in a forward rotation direction to correct the position of the pointer. 
 
     
     
       6. The pointer device according to  claim 1 ,
 wherein the at least one processor is configured to correct the position of the pointer by moving the position of the pointer by one step. 
 
     
     
       7. The pointer device according to  claim 1 ,
 wherein the stepping motor comprises a rotor having a magnet, and 
 wherein the at least one processor is configured to:
 determine whether the pointer is shifted in the direction due to the impact based on a polarity of the magnet; and 
 correct the position of the pointer. 
 
 
     
     
       8. The pointer device according to  claim 7 ,
 wherein the at least one processor is configured to output a pulse to the coil, and determine the polarity of the magnet based on a value of a current flowing through the coil. 
 
     
     
       9. The pointer device according to  claim 8 ,
 wherein the stepping motor comprises:
 a first coil configured to detect a peak of the electromotive force; and 
 a second coil configured to input a drive pulse and determine the polarity. 
 
 
     
     
       10. The pointer device according to  claim 9 ,
 wherein the at least one processor is configured to alternately put the first coil and the second coil in a high impedance state. 
 
     
     
       11. The pointer device according to  claim 1  further comprising a pointer position detection unit,
 wherein the pointer position detection unit comprises a light emitting element, a light receiving element, and a wheel train mechanism, 
 wherein the light emitting element is configured to emit light to a light transmitting portion of the wheel train mechanism, and 
 wherein the light receiving element is configured to receive the light transmitted through the light transmitting portion to detect a rotational position of the wheel train mechanism and correct the position of the pointer. 
 
     
     
       12. An electronic watch comprising the pointer device according to  claim 1 . 
     
     
       13. A control method for a pointer device, the pointer device comprising:
 a pointer; 
 a stepping motor comprising a coil and configured to drive the pointer; 
 a driving circuit configured to drive the stepping motor; 
 a detection unit configured to detect electromotive force generated in the coil due to an impact; and 
 at least one processor configured to control driving of the driving circuit, the control method comprising, the at least one processor performing:
 determining a direction of a first peak of the electromotive force detected by the detection unit; 
 determining a total number of a second or subsequent peaks of the electromotive force detected by the detection unit, wherein each of the second or subsequent peaks of the electromotive force is a peak in the opposite direction to a peak immediately preceding the each of the second or subsequent peaks; 
 determining whether the total number is an even number; 
 determining whether the pointer is shifted in a shifting direction corresponding to the direction of a first peak of the electromotive force based on the direction of the first peak of the electromotive force and a result of the determination of whether the total number is the even number; and 
 upon determining that the pointer is shifted in the shifting direction, correcting a position of the pointer in accordance with the shifting direction. 
 
 
     
     
       14. A non-transitory computer-readable recording medium storing a program for controlling a pointer device,
 a pointer; 
 a stepping motor comprising a coil and configured to drive the pointer; 
 a driving circuit configured to drive the stepping motor; 
 a detection unit configured to detect electromotive force generated in the coil due to an impact; and 
 at least one processor, wherein the program causes the at least one processor to execute:
 determining a direction of a first peak of the electromotive force detected by the detection unit; 
 determining a total number of a second or subsequent peaks of the electromotive force detected by the detection unit, wherein each of the second or subsequent peaks of the electromotive force is a peak in the opposite direction to a peak immediately preceding the each of the second or subsequent peaks; 
 determining whether the total number is an even number; 
 determining whether the pointer is shifted in a shifting direction corresponding to the direction of a first peak of the electromotive force based on the direction of the first peak of the electromotive force and a result of the determination of whether the total number is the even number; and 
 upon determining that the pointer is shifted in the shifting direction, correcting a position of the pointer in accordance with the shifting direction.